The Department of Special Investigation (DSI) is moving quickly to respond to a request by prosecutors to provide more information on the 2014 killing of Karen activist Porlajee "Billy" Rakchongcharoen.
DSI director-general, Pol Lt Col Korrawat Panprapakorn said he has instructed investigators to work quickly to find additional information.
On Sept 9, the Office of the Attorney-General (OAG) asked the DSI to furnish additional information in key areas in the Porlajee case which prosecutors still have queries about.
They include the test to ascertain the bloodline connection between Porlajee and his mother, the use of special instruments in examining the bone fragments believed to be those of the activist and the forensic results on the bones.
Two years ago, skull fragments, which the DSI determined to be Porlajee's, were retrieved from Kaeng Krachan reservoir in Phetchaburi.
An OAG panel has said there was not enough evidence to determine if the bone fragments indeed belonged to Porlajee.
As a consequence, there was insufficient proof to link four suspects -- Chaiwat Limlikit-aksorn, a former head of Kaeng Krachan National Park, and Bunthaen Butsarakham, Thanaset Chaemthet, and Kritsanaphong Chitthet -- to Porlajee's disappearance and murder, according to the prosecutors.
The evidence included a DNA test on the skull fragments believed to be Porlajee's, which the DSI insisted was a match to his mother's DNA. However, the prosecutors felt more information and evidence were needed to back the DSI's investigation.
In the meantime, prosecutors dropped the most serious charges including murder against Mr Chaiwat and the three others.
The DSI had recommended that prosecutors press up to eight charges against the officials and also filed its disagreement with their decision not to indict them for murder.